The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory captions and links exemplifying features within the Earth system. The community is invited to contribute digital imagery, short captions and relevant links.

Joshua Trees

Joshua trees (Yucca brevifolia) are distinctive desert plants throughout parts of California, Nevada, Arizona and Utah. They grow at elevations between 1,300 and 5,900 ft (400 and 1,800 m) and may reach 49 ft (15 m) in height and often occur as forests (bottom photo). Most prominent in California’s Mojave Desert, they're especially abundant in the Mojave National Preserve. Joshua trees can live for hundreds of years. Although tree-like in appearance they're not trees in the usual sense. Their trunks and branches are fibrous but they don't develop annual growth rings.

Reproduction is through symbiosis with the yucca moth. It pollinates the Joshua trees and lays its eggs on the stamen. As the grubs grow, they eat some of the developing plant seeds. Without the moths, Joshua trees couldn't propagate, and without the Joshua trees, yucca moths would have no place for their eggs.

Joshua trees are an indicator species. If you see one, you're in the Mojave Desert! Photos taken on March 11, 2017, along Cima Road, in San Bernardino County, California, elevation of 5,040 ft (1536 m). The strapping lad (Nick Keesey) in the top photo gives an idea of a typical Joshua's size.